At present, the techniques applying to the distributed disturbance and stress sensing of long-distance have some methods such as the laser interference method, phase sensitivity optical time-domain reflectometry method and polarization sensitivity optical time-domain reflectometry method. All these traditional methods have been limited to sensing distance less than 80 km, the low spatial resolution (>10 m), discrete single points and so on.
This invention combines the techniques of the polarization feature analysis and controlling with the Optical Frequency Domain Reflectometry (OFDR), and provides a polarization sensitive OFDR(P-OFDR) technique and the related device and related demodulation method.
OFDR technique presently known have been used in the field of optical fiber communication network testing disturbed stress and temperature sensing, etc., OFDR technique use the high-coherent laser to achieve high-speed and linear wavelength scanning, and the reference arm is coherent by the reflected light of Faraday reflector and single-mode optical fiber backscattering light (i.e. Rayleigh reflected light). Since the two lights have different optical paths, the two arm lights with different frequency are interfered to form beat-frequency at the interference end. The beat inference in the interferometer between the testing light (such as Rayleigh backscattering) and reference light. By using Fast Fourier Transform (FFT) to process detecting the beat-frequency signals, the backscattering information in different position of the sensing optical fiber can be obtained and then the sensing values can be obtained distributed backscattering information.